Working with MattesMattes are filters that you shape to define which areas of opaque video clips are to be made transparent during compositing. For example, you could use a circular matte to isolate a clock face from its background, or you could create a matte in the shape of a keyhole to simulate peeking through a keyhole in a door.Final Cut Express offers many types of matte filters (Figure 16.17 ). "Garbage mattes" are used to quickly rough out large areas of the frame. A key is a type of matte that uses a clip's color or luminance information to determine which opaque areas will be made transparent (bluescreen effects are created with color key mattes set to make blue areas transparent). You can combine layers of different types of mattes to create very complex composite shapes. Figure 16.17. Final Cut Express offers a toolbox full of special-purpose matte and key filters. When you create multilayer compositions, use these filters to mask out portions of the frame.
Travel mattesA travel matte allows one video clip to play through another. The alpha information in a third clip is used as a matte that defines the transparent and opaque areas of the composited image.When you create a travel matte effect, there are usually three video tracks involved; this is sometimes called a "matte sandwich." The background clip is placed on V1, or the lowest video track available. The matte clip, preferably a high-contrast, grayscale motion clip or still image, goes on the video track just above the background clip, on V2; and the foreground clip sits on V3, or the video track above the matte clip. A Composite mode specifically for creating travel mattes, called Travel Matte - Luma, is applied to the foreground clip. If the matte clip is placed on video track V1 without a background clip, then the background is automatically black.To create a travel matte:
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